* Add Japanese locale (ja) support - New: ja.ts with 2624 UI translation keys - New: ja.settings.ts with 1789 settings translation keys - Registered ja in runtime.ts (Locale type, LOCALES, LOCALE_LABEL_KEYS, normalizeLocale) - Added ja-JP BCP-47 mapping in intl.ts - Added JA_MESSAGES in bootstrap.ts - Added ja to lazy-load dictionary map in store.ts - Updated messages.test.ts with ja dictionary - Added common.language.japanese to all 8 existing locale files * fix(i18n): complete Japanese locale updates * test(i18n): enforce locale key parity * docs: add Japanese documentation --------- Co-authored-by: yuchi0531 <yuchi0531@users.noreply.github.com> Co-authored-by: Bohdan Triapitsyn <artmore@protonmail.com>